Research article
Volume 1 Issue 1 - 2014
Dissolution Profiles of Diclofenac Potassium Tablets from the Argentinean Market
Faculty of Pharmacy and Biochemistry, University of Buenos Aires, Argentina
*Corresponding Author: Adriana I Segall, Chair of Quality Medicines, Faculty of Pharmacy and Biochemistry, University of Buenos Aires, Junín 956 (1113) CABA, Argentina.
Received: November 11, 2014; Published: December 9, 2014
Citation: Luciana Petrone., et al. “Dissolution Profiles of Diclofenac Potassium Tablets from the Argentinean Market”. EC Chemistry 1.1 (2014): 2-8.
Abstract
In this study, the aim was to apply different comparison methods to dissolution profiles of immediate release commercial tablets of diclofenac potassium. Diclofenac potassium is classified as a class II drug as per the biopharmaceutical classification system. Dissolution testing was conducted using the USP monograph of diclofenac potassium tablets. All brands fulfil the specifications of dissolution test of USP comparison of dissolution profiles were carried out model independent approaches. Results show that there was no significant difference in dissolution efficiency and mean dissolution time between the reference product and Brands II, IV, V and VI. Using fit factors, only Brands I, II and V were similar.
Keywords: Essential oils; Vehicles; Doses; Arthritis; Migraines
Abbreviations: MDT: Mean Dissolution Time; DE: Dissolution Efficiency; SD: Standard Deviation; CV: Variation coefficient
Introduction
Diclofenac is commercially present as sodium and potassium salt in tablets for oral administration and as diethylamine for topical application. While extensive literature is available for sodium salt [1-3], little has been reported on the potassium salt [4].
Diclofenac potassium has excellent antipyretic, analgesic and anti-inflammatory properties. Diclofenac potassium is claimed to dissolve faster and hence absorbed faster than sodium salt. It is also indicated for the treatment of primary dysmenorrhea and mild to moderate pain [5].
Diclofenac potassium is classified as a class II drug as per the biopharmaceutical classification system (BCS) [5]. The poor dissolution rate of water-insoluble drugs is still a major problem confronting the pharmaceutical industry. Fini et al. [6] studied the dissolution efficiency of diclofenac salts prepared using alkaline metals hydroxide or organic aliphatic bases.
In recent years, more emphasis has been placed on dissolution testing within the pharmaceutical industry and correspondingly, by regulatory authorities. As a result FDA, EMA and WHO [7-9] provide recommendations to compare dissolution profiles. A dissolution profile is defined as the measured fraction (or percentage) of the labelled amount of drug that is released from a dosage unit (tablet or capsule) at a number of predetermined time points when tested in a dissolution apparatus, such as the US Pharmacopeia (USP) I or II dissolution systems. The FDA suggest some acceptable approaches for establishing similarity of dissolution profiles, such as the model-independent and model-dependent approaches, although any approach would be considered once it had been justified.
Although immediate release solid dosage forms are routinely subjected to test such as content uniformity, weight, hardness, friability and disintegration, the test that is most often associated with the assessment of in vivo performance is the dissolution test. Methods for comparing in vitro dissolution profiles can be classified into three main groups: ANOVA-based statistical methods, model-independent and model-dependent approaches.
ANOVA-based methods do not rely on curve fitting procedures and the dissolution data are used in their native form or as a simple transform and the analysis is capable of showing differences between profiles in level and shape. The latter characteristic is especially important with respect to learning about differences in the dissolution mechanism. The characterization as model-dependent method or model-independent method depends on the values which are used to perform the calculation. A model-independent method uses the dissolution data in their native form. The model-dependent methods, however, are based on different mathematical functions, which describe the dissolution profile. Once a suitable function has been selected, the dissolution profiles are evaluated depending on the derived model parameters [10].
The aim of the present study was to evaluate and compare the dissolution profile of six commercial products containing Diclofenac potassium 50 mg. marketed in Argentina, based on their in vitro dissolution characteristics using USP Test, Apparatus 2 [11]. Each formulation was compared with the reference using model-independent methods: fit factors, mean dissolution time (MDT) and dissolution efficiency % (DE).
Materials and Methods
Reagents
Analytical grade monobasic potassium phosphate (Anedra, Argentine) and sodium hydroxide (Mallinckrodt, USA) were used. Diclofenac potassium was purchased in Saporiti, Argentina, 99.9% calculated with reference to the dried substance, origin India.
Analytical grade monobasic potassium phosphate (Anedra, Argentine) and sodium hydroxide (Mallinckrodt, USA) were used. Diclofenac potassium was purchased in Saporiti, Argentina, 99.9% calculated with reference to the dried substance, origin India.
Materials
In our study, six commercial tablets containing Diclofenac potassium 50mg were purchased from pharmacies in Buenos Aires (Argentina). All tests were performed within products expiration dates.
In our study, six commercial tablets containing Diclofenac potassium 50mg were purchased from pharmacies in Buenos Aires (Argentina). All tests were performed within products expiration dates.
Apparatus and procedure
All dissolution studies were performed using USP37, Apparatus 2 in a Sotax AT7 (Sotax AG, Basel Switzerland), which is a manual-sampling dissolution bath. The diclofenac potassium tablets test was performed at 50 ± 1 rpm. The dissolution medium simulated intestinal fluid (without enzyme) pH: 6.8, at 37 ± 0.5°C. The acceptance criterion set was Q = 75 in 60 min.
All dissolution studies were performed using USP37, Apparatus 2 in a Sotax AT7 (Sotax AG, Basel Switzerland), which is a manual-sampling dissolution bath. The diclofenac potassium tablets test was performed at 50 ± 1 rpm. The dissolution medium simulated intestinal fluid (without enzyme) pH: 6.8, at 37 ± 0.5°C. The acceptance criterion set was Q = 75 in 60 min.
Dissolution media volume was 900 ml. In all experiments, 5ml sample aliquots were withdrawn at 10, 15, 20, 30, 45 and 60 min using micropipettes. The withdrawn amounts were adjusted in the calculations. All samples were filtered through filter paper (Whatman91; 10.0 µm). The filter paper used was properly validated using the standard solution and comparing with membrane filters. The amount dissolved was determined spectrophotometrically in a UV-VIS Spectrophotometer Cary 1E Varian (Victoria, Australia). The standard solution was prepared at the same concentration and in the same Medium. Twelve tablets or capsules of each preparation were studied to obtain statistically significant results.
Comparative dissolution
Model-independent methods
Fit factors: A mathematical comparison was performed by applying f1 and f2. These fit factors directly compare the difference between the percent drug dissolved per unit time for a test and a reference formulation.
Model-independent methods
Fit factors: A mathematical comparison was performed by applying f1 and f2. These fit factors directly compare the difference between the percent drug dissolved per unit time for a test and a reference formulation.
(1) Difference factor
(2) Similarity factor
Where n is the number of time points, Rt is the dissolution value of the reference formulation at time t and Tt is the dissolution value of the test formulation at time t.
(2) Similarity factor
Where n is the number of time points, Rt is the dissolution value of the reference formulation at time t and Tt is the dissolution value of the test formulation at time t.
The similarity factor (f2) is a logarithmic reciprocal square root transformation of the sum of squared error and is a measurement of the similarity in the percent (%) dissolution between the curves. Values of f1 between 0 and 15 and values of f2 between 50 and 100 are used to define equivalence of two dissolution profiles, which means an average difference of no more than 10% at the sample time points.
Dissolution efficiency: This concept was proposed by Khan and Rhodes [12] in 1975 and is defined as follows:
Where Q100 is the percentage of dissolved product, DE is then the area under the dissolution curve between time points 0 and T expressed as a percentage of the curve at maximum dissolution, Q100, over the same time period.
Mean dissolution time: The mean dissolution time is calculated from the accumulative curves of dissolved product depending on the time [13].
Where ti is intermediate time of the intervals of time sampled, ΔQi is the increase of the quantities of product dissolved in every interval of t considered and Q∞ is the maximum of product dissolved.
The results of DE and MDT of the different Brands of Diclofenac potassium tablets were compared with the reference using a two-variable t test as follows:
Where
and
are means of the model parameters of the reference and test products, respectively, nR and nT are the number of measurements for the mean and , and Sd is the weighted average standard deviation as shown below
and are means of the model parameters of the reference and test products, respectively, nR and nT are the number of measurements for the mean and , and Sd is the weighted average standard deviation as shown below
Where SR and ST are the standard deviations of model parameters for the reference and test products. If the calculated t values is less than the critical value of t (1- α/2, nR+nT -2), the two means and differ only randomly at risk level α.
and differ only randomly at risk level α.Results and Discussion
Dissolution of drug from oral solid dosage forms is a necessary criterion for drug bioavailability (i.e., the drug must be solubilized in the aqueous environment of the gastrointestinal tract to be absorbed). For this reason, dissolution testing of solid oral drug products has emerged as one of the most important performance test for assuring product uniformity and batch to batch equivalence. Variations of the pharmacopeia limits indicate unacceptable products.
| Brand | Other Ingredients | Appearance |
| I | Tricalciumphosphate, sodiumstarchglycolate, colloidalsilicondioxide, maizestarchmagnesiumstearate, povidone K-30, microcrystallinecellulose, cellacefate, diethylphthalate, titaniumdioxide, amaranth red aluminiunlake, tartrazinealuminiumlakeand talc | Brown, circular |
| II | Lactose, cross-linked carboxymethylcellulose, silicon dioxide, magnesium stearate, sunset yellow aluminum lake, titanium dioxide, dextrose, lecithin, potassium aluminum silicate, microcrystalline cellulose | Orange, circular, with indented line in center |
| III | Coprocessed lactose and microcrystalline cellulose, lactose monohydrate, sodium starch glycolate, magnesium stearate, silicon dioxide, talc, Poly(methacrylic acid-co-ethyl acrylate) 1:1, polyethilene glycol 6000, polysorbate 80, triethyl citrate, titanium dioxide, talc, iron (III) oxide yellow. | Yellow, circular |
| IV | Lactose, coprocessed lactose and microcrystalline cellulose, sodium starch glycolate, magnesium stearate, cellulose aceto phthalate, polyvinylpyrrolidone-vinyl acetate copolymer, polysorbate 80, titanium dioxide, diethyl phthalate | White, circular |
| V | Lactose monohydrate, coprocessed lactose and microcrystalline cellulose, sodium croscarmellose, magnesium stearate, hydroxypropyl methylcellulose, propylene glycol, titanium dioxide, talc, brilliant blue lake. | Light blue, circular |
| VI | Magnesium stearate, sodium starch glycolate, coprocessed lactose and microcrystalline cellulose, distilled water, hydroxypropyl methylcellulose, polyethilene glycol 6000, talc, iron (III) oxide brown, iron (III) oxide red, titanium dioxide | Brown, circular |
Table 1: Formulation Compositions.
Table 1 summarizes the characteristics of the six products. The products were purchased from pharmacies in Buenos Aires (Argentina). All tests were performed within products expiration dates, which were similar among brands. In this study we defined Brand I as the reference product.
| Time (min) | Brand | Mean% | RSD | Lower Limit | Upper Limit |
| 10 | I | 56.3 | 26.0 | 29.9 | 81.3 |
| II | 55.4 | 11.3 | 53.8 | 65.1 | |
| III | 12.6 | 21.1 | 10.6 | 16.4 | |
| IV | 19.0 | 36.7 | 11.1 | 30.8 | |
| V | 48.3 | 15.4 | 42.5 | 63.2 | |
| VI | 50.8 | 18.1 | 34.5 | 62.1 | |
| 15 | I | 90.3 | 8.8 | 83.0 | 102.8 |
| II | 79.0 | 10.1 | 77.0 | 89.1 | |
| III | 23.6 | 18.0 | 19.4 | 30.5 | |
| IV | 29.9 | 23.5 | 22.4 | 41.3 | |
| V | 84.5 | 8.0 | 73.9 | 91.6 | |
| VI | 67.4 | 14.0 | 51.6 | 80.2 | |
| 20 | I | 96.8 | 3.1 | 93.6 | 100.5 |
| II | 93.9 | 11.2 | 80.3 | 101.8 | |
| III | 46.7 | 13.4 | 39.8 | 56.2 | |
| IV | 59.3 | 30.2 | 36.0 | 82.4 | |
| V | 88.3 | 3.5 | 84.1 | 92.7 | |
| VI | 82.7 | 11.3 | 67.8 | 95.9 | |
| 30 | I | 97.7 | 2.2 | 94.1 | 99.9 |
| II | 103.2 | 4.6 | 95.9 | 109.9 | |
| III | 80.1 | 15.1 | 67.6 | 98.6 | |
| IV | 82.6 | 14.2 | 64.8 | 96.3 | |
| V | 95.4 | 2.0 | 92.8 | 98.1 | |
| VI | 96.1 | 4.2 | 91.8 | 103.5 | |
| 45 | I | 98.4 | 2.5 | 95.8 | 101.6 |
| II | 105.0 | 2.5 | 101.7 | 108.3 | |
| III | 102.9 | 6.6 | 92.0 | 109.8 | |
| IV | 101.0 | 4.1 | 95.0 | 106.9 | |
| V | 102.3 | 4.5 | 98.2 | 110.6 | |
| VI | 101.1 | 3.8 | 96.5 | 107.5 | |
| 60 | I | 99.4 | 6.0 | 95.0 | 111.1 |
| II | 104.2 | 3.7 | 99.2 | 109.4 | |
| III | 107.2 | 4.1 | 100.9 | 114.0 | |
| IV | 104.5 | 4.4 | 99.7 | 113.2 | |
| V | 102.5 | 1.7 | 100.4 | 104.9 | |
| VI | 100.2 | 4.6 | 96.4 | 108.2 |
Table 2: Dissolution data and descriptive statistics of six brands of diclofenac potassium tablets.
In the dissolution test for diclofenac potassium tablets described in the American Pharmacopeia (United States Pharmacopeia 37) no less than 80% (Q+5%) should be dissolved in 60 minutes. Table 2 summarizes the mean percent dissolved at each time point, the relative standard deviation (RSD), and the upper and lower limits.
| Brand | M | SD | CV | t ex |
| I | 84.4 | 4.2 | 5.0 | |
| II | 82.6 | 2.7 | 3.2 | 0.2198 |
| III | 60.8 | 3.8 | 6.2 | 2.4326 |
| IV | 64.9 | 5.8 | 9.0 | 1.5781 |
| V | 80.4 | 0.8 | 1.0 | 0.5540 |
| VI | 79.3 | 4.4 | 5.5 | 0.4928 |
Table 3: Average (M), Standard Deviation (SD), Variation Coefficient (CV) and t experimental (tex) of Dissolution Efficiency % (ED).
| Brand | M | SD | CV | tex |
| I | 13.6 | 2.6 | 19.0 | |
| II | 14.6 | 1.8 | 12.5 | 0.1838 |
| III | 28.4 | 2.6 | 9.1 | 2.3422 |
| IV | 25.6 | 4.0 | 15.5 | 1.4694 |
| V | 16.0 | 0.5 | 2.9 | 0.5357 |
| VI | 16.8 | 2.7 | 16.1 | 0.4970 |
Table 4: Average (M), Standard Deviation (SD), Variation Coefficient (CV) and t experimental (tex) of Mean Dissolution Time (MDT).
The DE and the MDT values are a useful way to reduce each curve to a single number, which may be related to the dissolution rate constant. The average, the standard deviation (SD), the variation coefficient (CV) and tex of the DE data are presented in Table 3 and the MDT data are presented in Table 4. Test “t” with 95% confidence for 22 degrees of freedom was (tn-2,α: 0.05) = 2.0739. There is no significant difference among the reference product and Brands II, IV, V and VI for both determinations.
;)
Figure 1: Dissolution profiles of diclofenac potassium tablets.
Fit factors are important quantitative methods that have been recommended by FDA, EMA and WHO guidelines for industry for comparison of dissolution profiles (Figure 1). Results obtained from the test using Brand I as the reference are shown in Table 5. The similarity factor f2 is more sensitive in finding dissimilarity between dissolution curves than the difference factor f1, and the values of fit factors are dependent on the number of sampling time point chosen. According to FDA f1 values up to 15 and f2 values greater than 50 should ensure equivalence of the dissolution curves, indicating an average difference of no more than 10% at the sample time points. Based on this guideline, only Brand II and V seem to show a dissolution curve similar with the reference.
| Brand | Fit Factor | |
| f1 | f2 | |
| I/II | 6 | 58 |
| I/III | 35 | 18 |
| I/IV | 29 | 22 |
| I/V | 6 | 60 |
| I/VI | 9 | 45 |
Table 5: Fit Factors for the six brands of diclofenac potassium tablets based on the average of twelve tablets.
Conclusion
This study found variations in the dissolution profiles of diclofenac potassium tablets commonly available in Argentina. The analyzed products presented very distinct dissolution profiles, showing that the dissolution test may be formulation dependent. All Brands fulfil the specifications of dissolution test of USP 37, Q = 75 in 60 min. There is no significant difference (p = 0.05) among the reference product and Brands II, IV, V and VI for DE and MDT. Using fit factors, only Brands I, II and V were similar.
In conclusion, significant differences were seen between the in vitro dissolution profiles of diclofenac potassium tablets from various commercial preparations. Nevertheless, the potential impact of these results on the in vivo bioavailability would require further investigation.
Bibliography
- O´Connor KM and O Corrigan. “Comparison of the physicochemical properties of the N-(2-hydroxyethyl) pyrrolidine, diethylamine and sodium salt forms of diclofenac”. International Journal of Pharmaceutics 222.2 (2001): 281-293.
- Bartolomei M., et al. “Physico-chemical characterisation and intrinsic dissolution studies of a new hydrate form of diclofenac sodium: comparison with anhydrous form”. Journal of Pharmaceutical and Biomedical Analysis 40.5 (2006): 1105-1113.
- Su SF., et al. “in vitro and in vivo comparison of two diclofenac sodium sustained release oral formulations”. International Journal of Pharmaceutics 260.1 (2003) 39-46.
- Fini A., et al. “Diclofenac salts. I. Fractal and thermal analysis of sodium and potassium diclofenac salts”. Journal of Pharmaceutical Sciences 90.12 (2001): 2019-2057.
- Chuasuwan B., et al. “Biowaiver monographs for immediate release solid oral dosage forms: Diclofenac sodium and diclofenac potassium”. Journal of Pharmaceutical Sciences 98.4 (2009): 1206-1219.
- Fini A., et al. “Factors governing the dissolution of diclofenac salts”. European Journal of Pharmaceutical Sciences 4.4 (1996): 231-238.
- FDA Center for Drug Evaluation and Research. Guidance for the industry: dissolution testing of immediate release solid oral dosage forms. Rockville, MD, 1997.
- EMA Committee for Medicinal Products for Human Use (CHMP). Guideline on the investigation of bioequivalence. London, UK, 2010.
- WHO Technical Report Series. Multisource (generic) pharmaceutical products: guidelines on registration requirements to establish interchangeability. 2006. No: 937.
- Yuksel N., et al. “Comparison of in vitro dissolution profiles and a rationale for wide dissolution profiles by ANOVA-based, model dependent and independent methods”. International Journal of Pharmaceutics 209.1-2 (2000): 57-67.
- The United States Pharmacopeia. 37th ed. Rockville, MD; 2014. 2593-2594.
- Khan KA and CT Rhodes. “Effect of compaction pressure on the dissolution efficiency of direct compression systems”. Pharmaceutica Acta Helvetiae 47.10 (1972): 594-607.
- Aguilar Ros A., et al. “Parámetros amodelísticos: comparación de perfiles”. Biofarmacia y Farmacocinética, ejercicios y problemas resueltos. 1st ed. Barcelona, España: Elsevier España S L, 2008. 3-4.
Copyright: © 2014 Luciana Petrone., et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
